Immobilization of Cu，Zn，Cd and Pb in a multi-metal contaminated soil using biodegradable slow-release polymeric fertilizer

Pot experiments were conducted to study the effects of a biodegradable slow- release polymeric fertilizer containing nutrient elements NPK（ SRPFNPK） and a biodegradable slow—release polymeric fertilizer with the function of water absorption（ SRPFWA） on the phytoavailibility of Cu，Zn，Cd and Pb in the multi-metal contaminated weak alkaline soils. The results showed that nutrient content，organic matter content and enzyme activity of soils significantly increased，however，phytoavailability of Cu，Zn，Cd and Pb in soils treated with SRPFNPK and SRPFWA reduced by 92.32%-99.10%，81.15%-96.06%，53.95%-78.51% and 94.27%-99.05% respectively. Correlation analysis showed that the soil available phosphorus（ AP） ，organic matter contents（ OM） were negatively correlated with the amount of Cu，Zn，Cd and Pb available in soils. Furthermore，tomatoes on the soils treated with SRPFNPK and SRPFWA resulted in higher total marketable yields but less accumulation of heavy metals in various tissues of tomatoes. The contents of Cu and Cd in the fruits were significantly lower than the food safety standards and the maximum allowable amounts of contaminants in foods.